nonparamteric statistical tests for coherence differences

Sameer Walawalkar sameer at ANDREW.CMU.EDU
Wed Jun 20 22:50:33 CEST 2007

```Dear Eric,

I was trying to adapt the online tutorial for doing statistical
non-parametric tests for coherence differences.

After using freqstatistcs along the lines spelt out in the tutorial, when
in order to generate topoplots, I use the following command:

TFR_LLvsRR_050_500_cmb = TFR_LL_050_500_cmb ;
TFR_LLvsRR_050_500_cmb.powspctrm = TFR_LL_050_500_cmb.powspctrm -
TFR_RR_050_500_cmb.powspctrm ;

I get the following Matlab error:
??? Error using ==> minus
Array dimensions must match for binary array op.

Clearly this is because I have unequal number of trials for the between
trials case.
As shown by the following.
>>size(TFR_RR_050_500_cmb.powspctrm)
ans = 129   204     7    10
>> size(TFR_LL_050_500_cmb.powspctrm)
ans = 128   204     7    10

And;
>> TFR_LL_050_500_cmb
TFR_LL_050_500_cmb =

label: {204x1 cell}
dimord: 'rpt_chan_freq_time'
freq: [8 9 10 11 12 13 14]
time: [0.0500 0.1000 0.1500 0.2000 0.2500 0.3000 0.3500 0.4000
0.4500
0.5000]
powspctrm: [4-D double]
cumtapcnt: [128x7 double]
cfg: [1x1 struct]

Now, from my understanding, the non-parametric statistical testing itself
doesnt require equal trials (and the fact that freqstatistics worked
shows that part is o.k.). So there must be a way to plot the results
bypassing the error. What am I missing here?

Best,
sameer

On Fri, 1 Jun 2007, Eric Maris wrote:

> Hi Sameer,
>
>> I am looking for Wiki entry or tutorial for doing nonparamteric
>> statistical tests for coherence differences (both within trial and
>> between trials).
>
> At this moment, only coherence testing between trials is implemented.
>
>>
>> What I can get is
>>
> http://www2.ru.nl/fcdonders/fieldtrip/doku.php?id=fieldtrip:documentation:tu
> tori
>> al:statistics#3_permutation_tests_for_time-frequency_representations
>>   which describes how to do the same for TFRs.
>>
>> I am thinking of attempting using basically the same set of commands, but
>> substituting the correct procedure  for calculating coherences etc in the
>> steps shown is section 3. will that be proper?
>
> I don't know. Just have a try. My expectation is that copy-pasting will not
> be sufficient to get it running. On the other hand, I used the
> Fieldtrip-code for all the analyses on which is reported in our JNM-paper on
> coherence difference testing.
>
> I am aware of the fact that the tutorial could be improved with respect to
> the testing of coherence differences.
>
>
> Good luck,
>
>
> dr. Eric Maris
> NICI/Biological Psychology and
> F.C. Donders Center for Cognitive NeuroImaging
> University of Nijmegen
> P.O. Box 9104
> 6500 HE Nijmegen
> The Netherlands
> T:+31 24 3612651 (NICI)
> T:+31 24 3610754 (FCDC)
> F:+31 24 3616066 (NICI)
> E: maris at nici.ru.nl
> MSc Cognitive Neuroscience :www.ru.nl/master/cns/
>
>
>>
>>
>> sameer
>>
>> ----------------------------------
>> The aim of this list is to facilitate the discussion between users of the
> FieldTrip
>> toolbox, to share experiences and to discuss new ideas for MEG and EEG
> analysis.
>> http://www.ru.nl/fcdonders/fieldtrip.
>
> ----------------------------------
> The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.
>
>

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.

```